Embodiments of the present invention generally relate to telecommunications and more specifically to techniques for providing an enhanced refresh in a SIP network.
Voice-over Internet Protocol (VoIP) has become popular and prevalent for communications. When a communication between two peers occurs, a session is created for the communication. As VoIP networks evolve into large end-to-end networks, messages, such as session initiation protocol (SIP) messages, increasingly have to traverse a larger number of intermediate hops before reaching a final end point. With unpredictable IP network delays and packet loss, the chances of losing a SIP message are high. This occurs especially if user datagram protocol (UDP) or any other unreliable protocol is used to send messages. When a SIP message is lost, this may lead to a hanging SIP session. A hanging SIP session is a session on one side of the communication that a peer thinks is active but is not active on the other side.
To address the issue of hanging SIP sessions, session refresh mechanisms are used. A SIP session is refreshed by sending SIP messages periodically. Refreshes in SIP can be expensive particularly if there is no change to a session. SIP sessions may be refreshed by sending messages typically used in a dialog, such as UPDATE, RE-INVITE, OPTIONS/200 OK, etc. These in-dialog messages are sent as a ping to see if the session is still active. If a response is received, then it is assumed the session is active. These messages are typically bulky in that they include a full header and body (e.g. session description protocol (SDP) or extensible markup language (XML) information). This is because they were not designed for a refresh. Rather, they were originally designed to perform other functions and thus, the format and requirements for content to be included in the messages do not take into account a mechanism for a pure refresh. For example, an INVITE message is typically used to request a connection to a device. However, the INVITE message may be used to refresh a session in that the INVITE message is sent for a session and if a response is received for the INVITE message, such as a 200 OK message, it is assumed the session is active. SIP requires that the INVITE message include certain fields in the header and also an SDP.
Accordingly, parsing and transporting these messages just for a refresh purpose includes a lot of overhead. For example, a refreshes has to parse the entire header and SDP when the message is received. Also, transporting the messages results in significant network bandwidth consumption over time. Accordingly, the above method of refreshing sessions is processing-intensive and also uses valuable network bandwidth. Further, the processing resources/bandwidth used is magnified when the messages have to pass through other SIP devices, such as SIP servers and user agents participating in the session.